1. Field of the Invention
The present invention relates to an electronic control unit for use in an electrically powered appliance (such as an electric pump, for example), and more particularly to an electronic control unit having a board on which electronic components are mounted.
2. Description of the Related Art
Japanese Laid-open Patent Publication No. 6-260777 discloses an electronic control unit for controlling an electrically powered appliance. This electronic control unit comprises a board mounted with electronic components and a case that accommodates the board. The case is filled with potting material, and the board and the electronic components are embedded in this potting material. By enclosing the periphery of the electronic components in potting material, this electronic control unit improves heat radiation away from the electronic components and prevents deterioration of the electronic components due to the external environment (such as moisture).
In this type of electronic control unit, the case is filled with potting material. Normally, the case is filled with potting material by pouring liquid-type (liquid-state) potting material into the case and allowing it to harden. With this method, though, bubbles can become trapped in the potting material during pouring. This can cause the electronic components to short or malfunction when the moisture contained in the bubbles condenses. For this reason, measures are taken to remove bubbles from the potting material after it has been poured into the case (by placing the electronic control unit in a vacuum chamber before the potting material hardens, for example). An opening is also provided in the case to allow air removed from the potting material during this process to be discharged outside the case.